Flu Scan for Nov 02, 2015

Flu A and B shedding patterns
Aussie flu vaccine effectiveness

Study finds shedding pattern differences between flu A and flu B

A 7-year study of naturally acquired flu infections revealed that viral shedding mirrors the clinical profile for influenza A infections, but not influenza B. A research group based in Hong Kong—where the study took place—published its findings Oct 30 in an early online issue Clinical Infectious Diseases.

The team followed initially healthy people from 2008 through 2014, identifying 224 influenza infections. For 127 of the patients they recorded clinical symptoms and monitored viral shedding with reverse-transcription polymerase chain reaction testing and viral culture.

In patients with influenza A infections, viral shedding peaked on the first 2 days of clinical illness, dropping to undetectable levels by day 6 or 7, a pattern that closely matched the illness trajectory. For influenza B, howeer, viral shedding peaked as soon as 2 days before symptom onset and lasted for 6 or 7 days after onset, with a bimodal pattern.

Researchers concluded that although clinical illness might serve as a proxy for influenza A, for influenza B, patients can be infectious before symptoms set in or after they improve.

The same team reported initial shedding findings for just 1 year, 2008. They noted that other shedding experiments involved high challenge doses and that studying naturally acquired infections may shed better light on the infectiousness period.
Oct 30 Clin Infect Dis abstract


Flu vaccine found 52% effective against hospitalization in Australia

Flu vaccination last year cut hospitalization for influenza by more than half in Australia, according to data released Oct 31 in Vaccine.

Researchers analyzed data from adult patients hospitalized with influenza from April to November 2014, which is Australia's flu season. They estimated vaccine effectiveness using data from 1,283 patients with flu and 1,116 patients who tested negative.

They found flu effectiveness at reducing the risk of hospitalization for flu to be 51.5% (95% confidence interval [CI], 41.6%-59.7%, P < 0.001) for all patients and 50.7% (95% CI, 40.1%-59.3%) in the target population.
Oct 31 Vaccine abstract

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